Our muscles are in a constant process of breakdown and regrowth at the rate of around 1-2 per cent per day. Take a look at your muscles; your bicep perhaps, or your sore calves from too much walking, or the muscles in your hand that can’t quite grip as strongly as they used to. In two to three months’ time, these muscles will have completely regenerated.
As bodybuilders know, this constant turnover of muscle protein provides a mechanism to not only maintain muscle mass but also to increase muscle strength and endurance. While increased dietary protein and exercise both stimulate muscle growth independently, the benefits are much greater when they are combined, and this strategy can be a potent countermeasure to muscular atrophy and muscle loss.
Why is this important to middle-aged and older men and women?
In order to stay strong as you age, your body needs to replace lost muscle mass, and the most effective way to do this is to provide your body with the building blocks of muscle tissue. Studies, including Tang et al 2009 and Burd et al 2012b, have shown that rapidly digested high-leucine content proteins such as high quality whey protein are remarkably effective in stimulating muscle protein synthesis. This has resulted in the “leucine trigger” hypothesis, in which it’s believed that consuming an amount of protein that contains sufficient leucine will provide a signal to the body to use that protein to repair and build muscle. Low leucine proteins, such as plant proteins, tend to contain insufficient amounts of leucine and therefore ineffective in stimulating muscle protein synthesis.
But there’s a catch.
As you age, it becomes increasingly difficult to repair and build muscle because your body’s ability to respond to the normal stimuli of increased dietary protein and resistance exercise becomes impaired. That’s why the emerging recommendations are to increase the amount of high leucine whey protein in your diet, with the consensus around 1.0-1.5g or protein per kg body weight per day.
This post was inspired by an example given by Luc van Loon, a Professor of Physiology of Exercise and Nutrition at Maastricht University Medical Centre in the Netherlands, to nutritionists, dieticians and food scientists from the Nutrition Society of Australia at a seminar in Melbourne.
1. Tang, JE et al J Appl Physiol (1985). 2009 Sep;107(3):987-92. doi: 10.1152/japplphysiol.00076.2009. Epub 2009 Jul 9.
2. Burd, NA et al Br J Nutr. 2012 Sep 28;108(6):958-62. doi: 10.1017/S0007114511006271. Epub 2012 Jan 31.